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Hi guys,
I am thinking about how to add a frequency display to my function generator project. The required range is 1 Hz to 100 kHz and if possible with a 1 Hz resolution. The source is square wave TTL level 50% duty.
And now the question; is this achievable using a 16FXXX device and the PBP PULSIN command?
Thanks!
Hi,
BPB calculates with 16 Bits ... Ok ???
100 000 Hz @ 1 bit resolution need ???
That's it ...
Alain
why do not use the timer ?
For low frequency is more accurate measure the period.
Regards
If using the PIC as the frequency generator, wouldn't it be simpler to calculate the frequency rather than measure it?
Alain> I don’t follow your discussion, sorry.
GioppY> Could you give more detail please?
Dave> I guess I was unclear about the use of the PIC, the PIC is not involved in the generator part.
Thanks!
Check you PIC datasheet, some have built-in counter. This allow you to use them to count the incoming pulses for a x sampling time.
A while back i've made this one
http://www.picbasic.co.uk/forum/showthread.php?t=1044
Maybe this could be handy for you. It use TIMER0
So, what you mean is that the PULSIN command is not the way to go then?
Thanks.
a 16F device running @ 20 Mhz max... so PULSIN will give you 2µs per count.Quote:
And now the question; is this achievable using a 16FXXX device and the PBP PULSIN command?
PBP 16F compiler uses 16 bits ... so, 65535 counts at a maximum
Pulsin will give you a valid result from 1 to 65535 unit +/- 1 count.
@ 50% duty cycle your period can be ... 4 to 131070 µs +/- 4µs
a 16F device running @ 4Mhz ... so PULSIN will give you 10µs per count.
PBP 16F compiler uses 16 bits ... so, 65535 counts at a maximum
Pulsin will give you a valid result from 1 to 65535 unit +/- 1 count.
@ 50% duty cycle your period can be ... 20 to 655350 µs +/- 20µs
from that you can understand what precision and resolution you can get with the PULSIN command.
That's quite simple ...
Alain
PS: Gioppy gave you ... half of the answer !!! LOL
Have a look here:
http://www.picbasic.co.uk/forum/show...69&postcount=4
You can use this code to measure the frequency with timer1. This open the timer1 gate for exactly 1 sec. (@4MHz); so you can get a resolution of +- 1Hz. The result return in 2 words Hicntr and Locntr. Obviously you need a routine that convert the 32 bit to decimal.
With a bit less accuracy can be done in pbp.
http://www.picbasic.co.uk/forum/showthread.php?t=7828
Not very easy, but works fine.
Regards
Gianni
Thanks Guys, I think I have enough to read up on for now! I’ll let you know how it develops.
All the best!